The invention relates to an x-ray diagnostic apparatus for producing transverse layer images of a radiography subject with an x-ray measuring arrangement comprising an x-ray source which produces a fan-shaped beam of x-rays penetrating the radiography subject, the cross-sectional extent of the beam perpendicular to the layer plane being equal to the layer thickness and in the layer plane being of a magnitude such that the whole layer is penetrated with radiation, and comprising also a radiation receiver which ascertains the transmitted radiation intensity, said radiation receiver being constructed as a circular ring into which the radiography subject may be inserted and consisting of a series of detectors, and with means for changing the direction of the x-ray beam's axis of symmetry, and with a computer for the transformation of the signals supplied by the radiation receiver into a layer image.
Described in U.S. Pat. No. 3,778,614 is an x-ray diagnostic apparatus which has all these features apart from the circular radiation receiver. In this known x-ray diagnostic apparatus, the radiation receiver is laterally displaceable. When the subject is scanned, lateral displacement movements and rotational movements through a prescribed angle, e.g. 1.degree., follow one another alternately until the entire subject is scanned. From the measured absorption values the computer calculates the transverse layer image in the form of a matrix of image point data. The drawback with this x-ray diagnostic apparatus is that, because of the necessary mechanical movement of the radiation receiver and the x-ray tube, the time required for an image exposure is relatively long.
In the publication "Computerized Tomographic Scanner" issued by American Science and Engineering, Inc., publication number ASE-3869, an x-ray diagnostic apparatus of the type stated at the beginning is described. This x-ray diagnostic apparatus thus has a circular radiation receiver which encloses the radiography subject. All that is necessary is a rotational movement of the x-ray source disposed inside the radiation receiver, but no movement of the radiation receiver. The time required for an image exposure is therefore reduced relative to the apparatus known through U.S. Pat. No. 3,778,614. Furthermore, a simpler mechanical structure also results.